In the past, whole blood transfusion in which all the components of blood obtained from blood donation are transfused has been the mainstream of blood transfusion. Recently, however, blood component transfusion has been practiced, attendant on the progress of technology, in which the blood obtained is separated into such components as red blood cells, platelets and plasma, and only the component or components needed by a patient are transfused. The blood component transfusion makes it possible to reduce the burden or side effects on the patient's circulatory system, while effectively utilizing the donated blood.
The blood (whole blood) obtained by blood donation, or a blood component prepared from the whole blood, is separated by centrifugation into a plurality of layers. For instance, when whole blood is centrifuged, the whole blood is separated into a light supernatant PPP (platelet poor plasma) fraction, a heavy precipitated CRC (concentrated red blood cells) fraction, and a buffy coat formed therebetween. When the buffy coat is centrifuged, it is separated into a supernatant component that contains platelets and leukocytes, and a precipitated component that contains red blood cells. When the residual component left after removal of leukocytes and platelets from whole blood is centrifuged, it is separated into a plasma layer as the supernatant component and a red blood cell layer as the precipitated component.
For separating whole blood into a plurality of blood components and containing and preserving the blood components in a plurality of preservation bags, or for further separating a blood component prepared from whole blood into a plurality of blood components and containing and preserving the blood components in a plurality of preservation bags, a blood bag system has been proposed in which a plurality of bags are interconnected by a plurality of tubes. An example of this blood bag system is described in U.S. Pat. No. 6,910,998. In such a blood bag system, for conducting predetermined blood treatments by switching over the communication states between the bags, clamps are provided for closing and opening the flow paths in the tubes. An example is disclosed in Japanese Patent Publication No. Hei 5-23792.
Such conventional clamps are each composed of a member possessing an overall flat C shape. The clamp includes a pair of pressing sections for pressing side surfaces of a tube, and an engagement section by which end portions of the C shape can be engaged with, and released from, each other. When the end portions are engaged with each other and the tube is pressed by the pair of pressing sections, the flow path in the tube is closed.